This invention relates to automotive safety restraint systems and, in particular, to an active three-point seat belt system with seat belt webbing having a thick webbing section such as an inflatable seat belt section.
Numerous designs of passive and active automotive occupant restraint systems are known for enhancing occupant protection in the event of a vehicle crash. Passive systems such as inflatable restraints or air bags and automatically deployed seat belt systems are known. Active seat belt systems have been use for many decades and are manually deployed by the occupant. The conventional seat belt system uses three points of connection with the vehicle structure and incorporates a lap belt section for engaging the occupant's lower torso and a shoulder belt section for engaging the occupant's upper torso. The seat belt restrains movement of the occupant in the event of a vehicle impact or rollover event. In order to enhance the comfort and convenience provided by the seat belt system, retractors are normally used which permit the belt webbing to be extracted and retracted onto the retractor, allowing movement of the occupant while maintaining the belt in close contact with the occupant. An inertia sensitive actuator locks the retractors when an impact or rollover event is detected, preventing extraction of webbing.
A more recent development in the area of seat belt systems is that of the so-called inflatable seat belt. An inflatable seat belt system incorporates a section of the seat belt which is inflated by a gas, typically by a pyrotechnic inflator, to increase its size and volume. Thus, when an inflatable seat belt is deployed, the normally narrow seat belt webbing expands significantly to reduce the contact pressure between the seat belt webbing and the occupant during a crash sequence. Inflatable seat belts also act as a belt pretensioner by reducing belt slack. Inflatable seat belts may utilize crash sensing systems also used to control other inflatable restraint systems to initiate inflation upon the detection of a vehicle impact or rollover event having predetermined dynamic characteristics.
Certain design constraints exist with regard to presently available inflatable belt systems. Since the inflatable belt section of the seat belt webbing is significantly thicker and bulkier than the remainder of the webbing, it is difficult to have the inflatable belt section pass through the three point belt “D” ring or seat belt tongue or roll into a retractor. Moreover, passing such a thicker segment of the belt would likely degrade occupant comfort. The webbing must ordinarily undergo a sharp bend and pass through narrow openings in the D-ring and tongue. These limitations set a practical limit on the thickness of the inflatable belt section of the belt webbing and require flexibility of the inflatable belt section. A similar problem would exist with a belt system which has a segment which is thicker or more bulky, designed to be oriented across the upper torso of the occupant, but which is not inflatable.
Seat belt webbing must be provided in a long length to enable a range of occupant sizes and seat positions to be accommodated. This is especially true where the seat belt anchorages are fixed to the body of the vehicle rather than the seat. In order that the thick belt webbing section, such as an inflatable belt section, is properly positioned at the upper torso area of the occupant, the inflatable belt section must ordinarily be long, and be capable of passing through seat belt hardware components, such as the tongue and D-ring and, in some cases, a retractor.
One approach to addressing shortcomings mentioned above is to use a three point restraint system having a fixed upper shoulder belt anchorage. Variations in the length of the webbing for different sized occupants or occupant movement would be accommodated through the use of a single retractor fixed to the lap belt portion of the webbing. Differences in the length of webbing for the shoulder belt portion would be taken up by allowing the webbing to freely flow through the buckle tongue. In this case, the thick seat belt portion would be maintained at the upper torso area of the occupant since it would also be fixed to the belt, at or near the upper seat belt anchorage. Although this approach would prevent the thick belt section from having to flow through the seat belt tongue, it would not provide the desired degree of comfort and convenience available through the use of dual retractor seat belt systems and would not ideally locate the thick belt section for all occupants. Comfort and ease of use are important factors in encouraging motor vehicle occupants to take advantage of the safety benefits provided by an active seat belt system.
In accordance with the present invention, a seat belt system is provided in which the position of the thick belt section, such as an inflatable belt section is controlled to be properly positioned on the upper torso area of the occupant, without the requirement that it pass through the tongue, D-ring, or other hardware components (such as a high mounted shoulder retractor). In a preferred embodiment, the belt system is implemented with a dual retractor system. Through a particular control system and sequence in which the two retractors are locked or allowed to freely retract or extend webbing, depending on whether the belt is being deployed or latched, causing the thick belt portion of the system to be maintained at a desired position on the occupant.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.